Bone fractures can occur due to a number of reasons: disease, such as osteoporosis; overuse by repetitive motion, which can, for example, cause stress fractures in athletes; trauma, such as by a fall or car accident; and the physiological changes that come with the aging process. An osteotomy is a surgical operation in which a bone is excised to shorten, lengthen or change the alignment of the bone. Osteotomies are often performed to correct bone deformities. Proper healing of both bone fractures and osteotomies can involve open reduction and internal fixation, where the bone fragments are repositioned in their normal alignment and then held together to facilitate healing.
A bone plate is a type of internal fixator that is surgically implanted and may generally be used to stabilize bone fragments and carry out osteosynthesis. For non-unions, such as joint fractures, simple shaft fractures and osteotomies, it is desirable that the bone itself supports and stabilizes rigid osteosynthesis. In cases of comminuted fractures, it is desirable that the bone ends be aligned and stabilized, while the proper length of the bone is maintained in flexible osteosynthesis.
Bone plates are often used to aid in the treatment of different bone fractures and osteotomies. Bone fractures, however, can be complicated, requiring treatment with more than one type of osteosynthesis. In one design, a bone plate can have a first set of holes for non-locking screws to achieve compression of the fracture site, and a second set of holes for locking screws to achieve fixed-angle fixation. One drawback of this type of plate is that it requires a large number of holes in the plate, which weakens the plate or requires a larger or thicker plate to compensate. In another design, a bone plate can have a combination of types of holes in a predetermined arrangement for receiving a locking screw or a non-locking screw. This plate still has the drawback of limiting the user to the type of receiving screw holes on the plate. In other words, certain parts of the bone plate can receive a locking screw for fixation, while other parts of the bone plate can receive a non-locking screw for compression. The user is not able to modify the location of the non-locking versus locking screws relative to the plate, and may have to utilize two or more plates to achieve the desired effect.
In general, bone plates may be utilized to carry out two different types of osteosynthesis, namely “rigid osteosynthesis” and “flexible osteosynthesis.” Rigid osteosynthesis is used for medical care of joint fractures, simple shaft fractures (where nailing is impossible) as well as for osteotomies. Aside from the possibility of anatomical repositioning, the bone itself supports and stabilizes the osteosynthesis, which allows for the possibility of putting stress on the extremity earlier and without pain. Additional advantages of the medical care of stable fractures can be observed when the blood circulation in the bone is greatly diminished due to trauma. For treating “nonunions” or in the case of existing infection, the fracture must be kept stable in order to make bone healing possible and so as not to irritate the infection further by instability of the fracture gap.
Flexible osteosynthesis, also known as “biological osteosynthesis,” may be desirable in the medical treatment of comminuted fractures in the shaft region of tubular bones. In the case of these fractures, it is an objective to maintain the proper length of the bone and to fix the bone ends (joints) in their proper anatomic positions with respect to one another. With flexible osteosynthesis, the fracture zone is not directly affixed or manipulated, and consequently, the blood circulation in this area is not inhibited. Bone plates designed for flexible osteosynthesis thus operate similarly to a locking, intramedullary nail, which is anchored only in the metaphyses.
Since fractures cannot always be treated with one type of osteosynthesis, surgeons must frequently compromise because a bone plate, which allows him to combine the two types of osteosynthesis discussed above, is not currently available. Such a combination would be beneficial, for example, when a joint fracture can be compressed with traction screws through the bone plate and the whole of the joint may be connected to the diaphysis over an internal fixative with angularly stable screws. Another illustrative application concerns porotic bones, where a bone plate with axially and angularly stable screws can be anchored in the metaphysial fragment, with a stable plate-affixation being undertaken in the diaphyseal range with the assistance of a plate traction screw through the fracture. A primary fracture stabilization can be achieved by this type of procedure.
This situation has led to the development and marketing of bone fracture fixators for both types of osteosynthesis. The two types of fixators, however, are designed specifically for their respective method. Thus, the disadvantages of these two systems lie in the difficulty in combining them. Accordingly, it is desirable to provide improved bone plates that allow for both rigid and flexible osteosynthesis. More importantly, what is needed is a bone plate that allows for use of both non-locking and locking screws within the same bone screw hole, in order to allow either fixation or compression, or both, at different locations on the same bone plate.